Thermoplastic webs have found application in many areas, for example as geomembranes to retain fluids such as water. Examples of typical uses of geomembranes are as liners in ponds, reservoirs, pits, canals and the like. Examples of such liner materials are described in U.S. Pat. No. 5,160,221 to Rohe, et. al. Additional uses for such membranes include protection from weather and the like, such as in roofing applications and other building applications. In many applications, very large sheets of thermoplastic webs are desired for use. However, the manufacturing size of the web is limited by the width of the available manufacturing equipment. For example, thermoplastic extruders are provided in widths up to 13 feet or so. As a general rule the wider the extruder, the more difficult it is provide a uniform thickness and desired quality of the web. When even larger webs than can be conveniently manufactured are needed for a particular application, separate web sections are often joined in a second step at a manufacturing facility or at the point of use in the field by adhering or welding separate sheets together. Field construction can be time consuming and challenging for many reasons, including the difficulty of handling large sections at the work site, the difficulty of keeping surfaces clean to provide good bonding, and the difficulty of providing a uniform and effective bond over long seams.
For several years, fabric mesh reinforced thermoplastic membranes have been available for use as a roofing membrane. The conventional way of making such membranes is to extrude molten thermoplastic onto one side of a fabric mesh to weld the fabric mesh to one side of the thermoplastic membrane. The resulting composite is then heated and a second layer of molten thermoplastic is extruded onto the other side of the fabric mesh to cover the fabric mesh and to weld the second thermoplastic to the first thermoplastic. U.S. Pat. No. 6,054,178 to Howells describes a method of manufacturing a fabric mesh reinforced monolithic thermoplastic membrane. The open mesh fabric is drawn into the gap between two calender rollers of a membrane extruder, a molten first thermoplastic material is extruded into the throat of the gap between the first roller and the first side of the fabric mesh, while a second molten thermoplastic material is simultaneously extruded into the throat of the gap between the second roller and the second side of the fabric mesh. The composite material is then drawn through the gap between the first and second rollers to force the molten first and second thermoplastic materials into and through the open mesh of the fabric to fuse and bond the molten first and second thermoplastic materials in and about the fabric mesh to form the fabric mesh reinforced monolithic thermoplastic membrane.
Configurations of roofing materials that are covering products comprising a membrane provided with and adhesive for adhering the covering product to a building structure are described in US Patent application Nos. 2004/0157074 and 2004/0191508 to Hubbard.
In the design of geomembranes for use in containment of fluids, such as liners for landfills, canals, ponds, and similar earthen constructions, a concern has been the tendency of material placed on top of the geomembrane to slide off of the membrane, particularly if the construction involves use of some angled berms or sidewalls as part of the containment structure. Another problem can be that the geomembrane itself slides off of the berm construction on which it is placed. Geomembranes have previously been prepared to purposefully provide one or both of the surfaces of the geomembrane with a large number of projections or recesses by embossing the geomembrane to improve the friction coefficient between the surface of the geomembrane and an adjoining surface. U.S. Pat. No. 5,728,424 describes systems and processes for providing the surface of a geomembrane with a textured surface. In this patent, systems and processes for applying particles or projections onto a surface of a geomembrane are described so as to improve the friction coefficient between the surface of the geomembrane and an adjoining surface. Similarly, methods for imparting antislip surfaces to various thermoplastic products, such as geomembrane sheets and liners, including landfill friction sheet and landscape reshaping restraints, are described in U.S. Pat. No. 6,509,084. Likewise, a geomembrane construction comprising a unitary structure fabricated by co-extrusion including a center core, a thermoplastic adhesive layer secured on one side of the center core, and a textured layer secured on the opposite side of the center core is described in U.S. Pat. No. 6,524,029.
It has also been noted in an article by the PVC Geomembrane Institute that                Many PVC geomembranes are manufactured with a smooth side and an embossed side. The embossed side surface usually resembles a file and is called a “faille-finished” surface. Accordingly, a faille PVC geomembrane interface is one in which the faille-finished surface of a PVC geomembrane is sheared against another geosynthetic component. Test results indicate that the smooth side of the PVC geomembrane yields a larger interface shear resistance than the faille-finished side due to the higher flexibility and larger contact area of the smooth side. Since the faille side of a PVC geomembrane renders a lower interface shear resistance than the smooth side, it was deemed appropriate/conservative to compare the shear strength of the faille PVC geomembrane interfaces to the HDPE and VFPE geomembrane interfaces.See internet site for pgi-tp.ce.uicu.edu Technical Files.        